Lubricant



2009 F. to 350 F. during normal operation. m1

' Patented June 24, 1941 LUBBIOAN T Edwin .lQBarth, Chicago, Ill, assignor to Sinclair Refining Company, New York, N. Y a corpora tion of Maine No Drawing. Application April 29, 1938, 1 Serial Iva-205,003

\ 6 Claims. (Cl. 252-46) This invention relates to the compounding of petroleum oils, and more particularly to improved compounded petroleum hydrocarbon oils containing novel addition agents which improve the physical characteristics and lubricating propen-. ties of petroleum lubricating oils.

The bearing surfaces of internal combustion engines and the like have, until comparatively recently, been constructed of Babbitt metal, a material enjoying the advantage of being highly resistant to corrosion. The present trend of the industry is toward the substitution of other alloy bearing metals capable of withstanding higher loads per unit of area such as copper-lead alloys and cadmium-silver alloys for the previously used Babbitt metal.

Advances in this direction have been handicapped by the fact that many lubricating oils are seriously corrosive with respect to these newer types of alloy bearings. The corrosive characteristics of lubricating oils are therefore of particular importance because of the present trend toward the substitution of other alloy-bearing metals for the previously used Babbitt metal.

As any corrosive action of lubricating oils in creases markedly 'with increasing'temperatures, it presents a peculiarly serious problem where, as

in many internal combustion engines, the lubricating oil temperatures frequently are as high as e seriousness of the problem can be illustrated by example: A highly refined Pennsylvania motor oil which,. at an operating temperature of 350 efl'ected a loss by corrosion of only 0.4 milligram of a Babbitt bearing in 24 hours, eflectecla loss by corrosion of 2012 milligrams of a cadmium-- silver bearing under similar operating conditions in the same period.

Certain addition agents have been suggested heretofore which, when incorporated in petroleum lubricating oils, reduce the corrosive na--" .ture of the oil. It has been generally characterthermore, the oil must have a film strength sufli- 'cient to insure efiicient lubrication of the engine and to eliminate the possibility of scoring 01 moving parts caused by'the breakdown of the lubricating film between these moving parts.

Petroleum lubricating oils frequently havea v tendency to deteriorate merely-as a. matter of time and such tendency is usually more .pro-

nounced under conditions 01' use, particularly where the oil is maintained at an elevated temv perature for prolonged periods. Such deteriora: tion becomes serious and results in' serious changes in the composition and characteristics of v the oil when the oil is used for lubricating internal combustion engines such as are employed in modern automobiles andaeroplanes where the oil is in contact with rapidly moving and highly heated engine parts. Such deterioration of lubricating oil is characterized, in one aspect, by the formation of heavy sludge which tendsto collect in the oil pump and oil lines of themgine and eventually to clog them to such an istic of such addition agents, however, thattheir only beneficial efiect upon the lubricating oil is a reduction of the corrosiveness of the oil, and many such addition agents have a deleterious efiect upon other .desirable properties of the oil. v

'01 the numerous prerequisites of apetroleum lubricating-oil satisfactory for use in internal combustion engines, in addition to the requirement that they be substantially non-corrosive, two are of major importance. The oil must be extent as to prevent or greatly impair the eiii-- Q cient lubrication of the engine. This deterioration further causes an increase in the viscosity of the lubricating oil i'urther tending to impair proper lubrication'and subjecting the engine to a correspondingly increased load.

The film strength 01' these lubricating oils is of particular importance because of the high and:

increasing pressures encountered between moving parts of internal combustion engines. A high film strength promotes the complete protection of moving parts by insuring the presenoe'of a film of the lubricating oil between these moving parts. A breakdown oi such a film due to inferior film strength results in the scoring and undue wear of adjacent moving parts. q I have discovered that the corrosive nature of petroleum lubricating oils may be markedly reduced to the point of -substantial elimination'by incorporating in such oils a small proportion of oil-soluble disulphides of an aliphatic hydrocarbon" substituted phenolcontaining 12 carbon atoms. Such disulphides comprise the isomeric disulphides of lauryl phenol.

Appropriate disulphides may be prepared in accordance with my invention by reacting the allphatic hydrocarbon, substituted phenol with sulhur monochloride. The immediate product of this reaction is the di-oiwsulphide of the phenol. The di-oxysulphide is somewhat unstable and tends partially to rearrange and form the true disulphide of the phenol. The incorporation in a petroleum lubricating oil 01' a sniallpropdrtion of either the di-oxysulphide or the true disulphide of the aliphatic hydrocarbon substituted phenol, or a mixture of these compounds, not only re- 'duces the corrosiveness of the oil but has the further salient advantages of improving the stability of the oil as shown by an increase in the sludging time of the oil and of increasing the film strength of the oil as indicated by an increase in the breakdown point of the'oil.

Inasmuch as the two forms of the disulphide ofthe aliphatic hydrocarbon substituted phenol appear to exist in equilibrium with one another,

with the equilibrium controlled as described further herein, the disulphide will generally comprise 'a. mixture of both disulphides with one or the other 'of the disulphides predominating in the mixture. These disiilphides greatly diminish the corrosiveness of petroleum lubricating ofls regardless of which disulphide predominates in the mixture or regardless of which disulphide is used in a substantially pure form. The predominance of one or the other of the disulphides is of importance in that the two forms have somewhat diflerent effects upon the stability and film strength of the oil. The expression ad dition agent as used herein is intended to mean either form of the disulphide or intermediate 'mixtures of these disulphides, unless otherwise defined. I

The amount of the addition agent necessary to produce the desired result varies to some extent with the nature oi the oil treated. The more corrosive oils, generally speaking, require the addition of a greater amount of the addition agent than do the less corrosive oils. The optimum amount of addition agent to' be used will also vary with the temperature conditions and the particular bearing metal with which the oil: is to be used. poration of not more than about 1% of the addi- I have found that the incortion agent is usually sumcient, although other amounts between approximately 0.1% and 3.0% may-be used with advantage.

The use of the particular disulphide predomimating in either form of arrangement is governed to some'extent by the physical properties of the petroleum lubricating oil, other than its corrosiveness, which it is desired to improve. In genera], the di oxysulphide is more effective in increasing th film strength of the oil than is the true disulphide. On the other hand, the disulphide is generally superior to the di-oxysulphid'e in-its effect as a stabilizer of the lubricating oils. These addition agents are readily soluble in petroleum lubricating ofls and may be added by any convenient means designed to disperse them thoroughly throughout the oil such, for example, as by stirring. When a comparatively large amount of an addition agent is to be incorporated in the oil the incorporation may be facilitated by warming the oil, although it is generally unnecessary to resort to this procedure.

The addition agent used in accordance with my invention maybe prepared'by treating .the aliphatic hydrocarbon substituted phenol wit-h vsulphur monochloride with the formation of the di-ox ysulphide of th phenol. A substantial rearrangement of this product may be effected by treating the product with an alkali, and then precipitating the jdisulphide' of the phenol by acidification of the alkaline solution of the .rearranged disulphide.

In preparing the di(lauryl' phenyl) di-Oxysulphide [(C1':H :sCuH4QS)g] referred to further hereinin' examples of my invention, 200 parts with simultaneous'evolution of hydrogen chloride gas. After the evolution of gas had substantially diminished, the reaction mixture was refluxed gently for a period. of approximately three hours until the Beilstein test for chlorine was negative. After a negative chlorine test was obtained, the benzol was carefully distilled off under-a high vacuum at the lowest possibletemperature leaving a residue which comprised di(lauryl phenyl) di-oxysulphide. The di(lauryl phenyl) di-oxysulphide is somewhat unstabl in that it tends to rearrange itselt to form di(lauryl phenol) disulphide. The residue of the distillation operation is believed, therefore, to comprise an equilibrium mixture of these two forms with the di(laury1 phenyl) di-oxysulphide predominating' The rearrangement of the di-oxysulphide was effected by dissolving the di-oxysulphide; obtained as the residue described above, in about 540 parts of a mixture of equal parts of alcohol and water made alkaline by theaddition of about 24 parts of sodium hydroxide. The solution of the sodium salt of the di-oxysulphide was treated with carbon dioxide whereupon an oily layer was precipitated from the solution. The separation 'of the oily layer from the aqueous layer was enhanced by the addition of benzol to the mixture whereupon a sharp separation of the oily constituent was obtained. The benzol solution of the oily constituent was subsequently thoroughly washed with water to remove the alkali. The neutral benzol solution was then subjected to a topping operation below F. under a high vacuum leaving a brown viscous oily residue which comprised di(lauryl phenol) disulphide This product contained 10.2% sulphur as compared with the theo'retical amount of 10.9% sulr phur calculated for di(lauryl phenol) disulphide. The phenol number of the brown oily product was 218, thus comparing favorably with the the oretical phenol number of 192 for di(lauryl phenol) disulphide. The brown oily product was found to contain a trace of free sulphur and may contain a substantial amount of di(1aury1-phenyl).

di-oxysulphide.

If it is desired'to remove the free sulphur from the di-oxysulphide or the disulphide of the pheblack precipitate isproducd. The solvent .benzol may then be removed from the 'dis'ulphides at a low temperature under a high vacuum. The residue ;of this distillation comprises thedisulphide substantially free from traces of -uncombined sulphur. An analysis of the di(laurylphenol) disulphide prepared as described above and purified, in accordance with. this operation indicated that the sulphur content of the purified produciPWas 9.03%.

It is apparent thatthe addition agents used in accordance with my inventionrnaycomprise either or both of the isomeric forms of the disulphide of the phenols. 'When the disulphide is prepared as described above, the firstform of the disulphide thus produced comprises the di-oxysulphide and may be incorporated directly in a lubricating oil before an appreciable amount of this product has been rearranged or it maybe incorporated in a lubricating oil after a portion of the product has spontaneously arranged itself as the true disulphide. n the other hand the di-oxysulphide may be substantially rearranged by treatment with an alkali and subsequent acidification, as described above, in which case the addition agent will be predominantly, if not substantially completely, in the form of the true disulphide. It should be noted that if the disulphide is prepared directly by means of some other method of production, the addition agent may comprise the tain physical characteristics of petroleum lubrieating oils; It must be understood that my invention is not to be'limited to the percentages and oils illustrated in these tables or to the particular "disulphides referred to therein. The values reported in these tables have been determined with the Sinclair bearing corrosion test machine for corrosion, by the Indiana method for stability and with the Faville-LeVally test machine for film strength. i

The Sinclair bearing corrosion test machine comprises a test chamber thecover portion of which comprises a lead alloy bath which may be heated by electrical resistance units; A shaft extends through the interior of the test chamber, and this shaft has four cross arms mounted at 90 to one another at spaced intervals along the shaft. The shaft is so positioned within the test chamberthat when the chamber is partially filled with a lubricating oil to be tested the cross arms dip into the oil as the shaft is rotated. The bearings to be tested are attached to a removable bar bearings are weighed, and the loss in weight of each bearing in each stage is reported in milligrams. A loss of bearing metal through corrosion as determined by the above test substantially in excess of 100 milligrams in either stage of the test indicates that the particular lubricating oil is excessively corrosive with respect to bearings of the type tested. Though it is desirable to reduce the corrosive action of the oil to a minimum it is usually suflicient for practical purposes that such action be so reduced as to effect a loss of t not substantially greater than 100 milligrams in positioned within the test chamber on one side wall thereof above the level of oil within the chamber. and each test bearing is attached to the removable bar at a point opposite each set of cross arms mounted on the shaft. As'the shaft is rotated a stream of the test oil is directed by each of the cross arms against each of the test bearings. Means are further provided for con-- tinuously passing air through the test chamber..

In addition to the temperature regulation pro-,

vided by the lead alloy bath in the cover portion of the test chamber, the chamber is partially subusing another set or weighed bearings. The test oil is maintained at 280 F the lead alloybath is maintained at a temperature of 430 F., and air is passed through the test chamber at the rate of one cubic foot per minute, Each set of bearings is removed after each stage of the test, these either stage .of the test.

The Indiana method of measuring the stability of lubricating oils in terms of the rate of sludge-formation has been described in the Society of Automotive Engineers Journal, vol. 34,

No. 5, page 1'72. According to this method the time is determined in which 10 milligrams of .sludge are formed in 10 grams of the oil maintained at a definite temperature while air is bubbled through the oil at a specified rate. This time, expressed in hours, is designated "sludging 'time and is a measure of the rate of sludgeformation in that particular oil under the particular conditions of the test. The term sludging time as used hereinafter refers to the abovedetermined measure of the rate of sludge formation and is a relative measure of the stability of lubricating oils under conditions of storage or use.

The oil had an A. P. I. gravity of 28.6", a viscosity of 445 seconds Saybolt at F., a viscosity index of 103.6, and a pour point of 5 F. The di(lauryl phenyl) di-oxysulphide comprised the product obtained as described above from which the traces of free sulphur had not been removed and appeared to contain a substantial amount of di(1auryl phenol) disulphide produced by the spontaneous "rearrangement of a portion of the di-oxysulphide. The corrosiveness of the uncompounded and compounded oil is indicated by the results of the bearing corrosion testv conducted as described above.

Table I Addition agent, percent None 0.3 1.0

First stage:

Sat-co, mgm. loss 2 2 Cu-Pb, mgm. loss 448 29 Cd-Ag. mgm. loss 1457 2 Second stage:

Satco, mgm. loss 28 6 Cu-Ph, mgm. loss 676 213 Cd-Ag, mgm. loss 1290 3 The results of this tabulation show that as littleas 0.3% by weight of the di(lauryl phenyl) dioxysulphide substantially eliminates the corrosiveness of this particular Pennsylvania motor I oil. The use of a larger quantity of the di(lauryl L. N300 n-wuoo phenyl) di-oxysulphide does not appreciably diminish the corrosiveness of the oil beyond the extent effected by the use of 0.3% of the addition agent.

Table II contains illustrations of the effect upon the corrosiveness of a Pennsylvania motor oil of varying amounts of the di(lauryl phenol) d1") sulphide. The oil comprised the same oil used in the tests reported in Table I. The di(lauryl phenol) disulphide contained traces of free sulphur and comprised the product obtained as described above from which the traces of free sulphur had not been removed. The corrosiveness of the samples is indicated by the results of the bearing corrosion test conducted as described above.

The results of this tabulation show that substantially th same reduction in the corrosiveness of this particular Pennsylvania motor oil may be effected with'the di(lauryl phenol) disulphide as with the di(lauryl phenyl) di-oxysulphide.

Table III shows the effect of varying proportions up to 0.3% by weight of the addition agent on another corrosive lubricating oil comprising a doublesolvent treatedPennsylvania motor oil having an S. A. E. number of 50. The addition agent used in these tests comprised di(lauryl phenol) disulphide prepared as described above including the elimination of free sulphur 'by treatment of the addition agent with purified mercury. The

bearing corrosion tests were conducted under the of the oil was eil'ected by the use of di(lauryl same conditions as those in Table I.

Table III I Addition agent, percent None 0.1 0.2 0.3

First stage:

Satco, mgm. loss 0 1 1 Cu Pb, mgm loss 320 I 340 27' Cd 899 559 14 Second.

Saco, mgm. loss. 5 7 B Cu-Pb, mgm loss 762 941 827 Cd-Ag, mgm. loss 1276 1253 60 Table 111 indicates that 0.3% by weight of the 6 addition agent is suflicient to diminish the corrosiveness of this particular oil to within practical limits. Smaller quantities than 0.3% by weight I have an appreciable eiTect on the corrosiveness of this oil although these smaller quantities do not 6 diminish the corrosiveness oi. the oil sufliciently for those instances where a strictly non-corrosive oil is demanded.

Table IV illustrates the efl'ect of-one of the addition agents upon the stability and film strength of a. lubricating'oil. The lubricating oil used in the tests recorded in Table IV was the same as' that used in connection with Table II. The addition agent comprised di(lauryl phenol) disulphide. The stability of the samples or oil is indicated by the sludging time of these samples. The sludging' time required to form 0.1% tar (sludge) was measured as described he'reinbetore, and the sludging time required to produce 1.0% tar was obtained under the same conditions except that the period was measured which was required for the formation of 1.0% sludge. The film strength of the samples-is indicated by the Favllle-LeVally breakdown point measured in As shown in Table IV the stability and film strength of this particular Pennsylvania motor oil are substantially increased by the incorporation therein of 0.3% by weight of the addition agents. It is thus apparent that [the use of 0.3% by weight of di(lauryl phenol) disulphide to obtain the most economical reduction in the corrosiveness of this particular on is further characterized by improvements in the stability and film strength of the oil.

Table V shows theeflect of di(lauryl phenyl) di-oxysulphide upon the film strength of a lubri- 5 eating oil. The lubricating oil and addition agent used in the tests recorded in this table 'were the same as those used in connection with Table I.

The film strength or .the samples is indicated by the .Faville-LeVally' breakdown point measured in pounds. As will be seen from this table the same increase in the film strength of the oil was obtained by the useof 0.1% as with 0.3%by

weight of the addition agent. It will also" be noted that a greater increase in the film strength phenyl) di-oxysulphide than was efl'ected by the use of an equal amount of di(laury1 phenol) -disulphide.

From the foregoing illustrations of the applicability andadvantages of'my invention it will 0 be seen that the use of a relativelyv small proportion of the dlsulphides oi. the aliphatic hydrocarbon substituted phenol containing 12 carbon atomsmarkedly diminishes the corrosiveness of corrosive petroleum lubricating oils without ad- 5 versely aflecting the'other physical characteristics of the oil. In fact, the incorporation 01' a small proportion .of the addition agents of my 'inventionfin these lubricating oils .efiects .,still 'further improvements in the physical chara'cteristicsoi the oils by increasing the stability and the film strength oi. the oils. The resulting compounded lubricating-oil is substantially free of any corrosive action 'upon'the bearings 01 an internal combustion engi'na'does not lose its valuable lubricating properties even after continued use at high temperatures, and insures complete lubrication of rapidly moving parts operating under high surface pressures.

The addition agents used in accordance with my invention may contain a small amount of free sulphur or may be purified to eliminate this free sulphur where the presence of the uncombined -sulphur is undesirable. The addition agents may comprise either the di-oxysulphide or the disulphide, or an equilibrium mixture of the two differently arranged forms. Furthermore, the addition agents may be used as the only addition agents in a lubricating oil or may be used in conjunction with other addition agents blended in the oil, in which case the addition agents of my invention will supplement and not deleteriously affect the properties imparted to the oil by the other addition agent or agents.

I claim:

1. An improved lubricating oil which comprises 2. An improved lubricating oil which comprises a petroleum lubricating oil containing an eflec- 'tive amount of the product obtained by reacting lauryl phenol with sulphur monochloride.

3. An improved lubricating oil which comprises a petroleum lubricating oil containing an efiective amount of av disulphide oi lauryl phenol.

4. An improved lubricating oil which comprises a petroleum lubricating oil containing an effective amount of the final product by reacting lauryl phenol with sulphur monochloride, rearranging the product of this reaction by treating the product with an alkaline solution, and precipitating the rearranged final product by acidification of the alkaline solution.

5. An improved lubricating'oil which comprises a petroleum lubricating oil containing an effective amount of di(lauryl phenyl) di-oxysulphide and di(lauryl phenol) disulphide.

6. An improved lubricating oil which comprises a petroleum lubricating oil containing an efiective a petroleum lubricating 011 containing an eflec- I tive amount of di(lauryl phenol) disulphide.

amount of di(lauryl phenyl) di-oxysulphide.

EDWIN J. EARTH. 

